Combustion of materials

ABSTRACT

The invention relates to combustion apparatus particularly aimed to dispose of materials which are normally difficult to completely burn. The apparatus has a refractory structure forming the combustion chamber into which the material to be burnt is fed. The material is subject to a current of forced air.

United States Patent 431/173X 431/173X 110/28 110/18A 110/18 110/7X l10/7X 110/18 ll0/7S 110/7 m mmmlmm m m m M mm m m u ne H u "as S n" .p .lk "0 am Mu h y t hCh e s m m m m P am a wh m o o u 1 c r ECCBDSVWBM 4494785778 3355556666 9999999999 1111111111 5585867026 11 4509 48854 6630340577 ,9 ,3 680 0405477 55070494500 ,fi 33 22223333 nl 6 9 0. 1 e a d m m u 7 W M 6 m m m R 9 M m:m 1 l I- or mw 2 7 u M 5 w .n 7 m w 696 mm m w mdfi n ,3 B mmmwoozqq m g nmwwao m MHE7FFFNG6 r. 0. d m mm 6 miwmwm M a n I AFPP 1 111] 1] 2 252 3 7 2243 33 l [[[l Primary Examiner-Kenneth W. Sprague Attorney-Shapiro and Shapiro [54] COMBUSTION OF MATERIALS o 0 19 lg n F [51] Int.Cl......,......

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ABSTRACT: The invention relates to combustion apparatus 73 ch are normally spose of materials whi particularly aimed to di difficult to completely burn. The apparatus has a refractory structure forming the combustion chamber into which the material to be burnt is fed. The material is subject to a current of forced air.

[56] References Cited UNITED STATES PATENTS 1,835,297 12/1931 PATENTEU FEB23 1911 SHEH 01 0f IMIIIIM I I I I I II.

I II II;

SHEET 0 2 OF PATENIED FEBZ 31am PATENTEDFEB2B|97| 3.565021 SHEET 030k 10 PATENIEDFEB23|97| 3565021 sum uunr 10 PATENIED FEB23 m SHEET 05 0F PATENTEnriazslsn v 3,565,021 saw our 10 PATENTEU :FEB23 19m SHEET 10 0F 1 COMBUSTION OF MATERIALS The present invention relates to the combustion of waste materials such as used oils e.g. used engine oil, used rubber tires and domestic and industrial refuse.

It is an object of the present invention to provide apparatus by which waste materials may be burned so as to produce a clean effluent. v v

The present invention provides combustion apparatus comprising a refractory structure defining a combustion chamber, means for forcing air into the chamber to provide a current of air therein, means for introducing fuel into the chamber; the air-forcing means and the fuel-introducing means being arranged so that fuel received into the chamber is subjected to the current of forced air. Preferably, the combustion chamber is of substantially circular cross section.

An advantage of the present invention is that it accom- 1 plishes a complete combustion of the waste material in the combustion chamber and therefore, produces an effluent free from gross desposits of carbon. The apparatus of the present invention is, therefore, eminently suitable for use as an incinerator of waste materials. However, because the effluent is clean, it may conveniently be used as a heating medium e.g. in a heat exchanger, and the apparatus of the present invention may, therefore, also be employed as a producer of useful heat.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which like parts are indicated by the same reference numerals and in which:

FIG. 1 is a perspective view of an oil-buming furnace installation according to the present invention;

FIG. 2 is a perspective view of the furnace employed in the installation of FIG. 1 shown in partly finished condition more clearly to reveal its structure;

FIG. 3 is a plan view of the combustion chamber of the furnace shown in FIG. 2;

FIG. 4 is a perspective view of an oil-metering device employed in the installation of FIG. 1;

FIG. 5 is a perspective view of an alternative oil-metering device;

FIG. 6 is a side elevation of the device of FIG; 5;

FIG. 7 is a perspective view of a further alternative oil-metering device; 7 v

FIG. 8 is a side elevation of amodified oil-collecting means for use in a metering device as illustrated in FIG. 7;.

FIG. 9 is a side elevation of a tire-burning; furnace installation of the present invention, with someof the FIG. in section revealed by broken away parts and with other hidden structure shown in outline; I f V Fig. 10 is a plan view of the furnace shown in FIG. 9, with hidden structure shown in outline;

FIG. 11 is a plan view of an alternative combustion chamber for the furnace shown in FIG. 9;

FIG. 12 is a perspective view of a refuse burning furnace installation of the present invention;

FIG. 13 is a perspective view of the interior of a combustion chamber of the furnace shown in FIG. 12, showing the interior aspect of refuse inlet and a forced air inlet to the combustion chamber; 7 7

FIG. 14 is a perspective view of a forced air inlet to the fun nace shown in FIG. 12;

FIGJS is a side elevation of a combustion chamber top for use in a furnace according to the present invention with hidden structure shown in outline;

FIG. 16 is a side elevation of an alternative combustion chamber top with hidden structure shown in outline;

FIG. 17 is a sectional elevation of a further form of furnace according to the present invention;

FIG. 18 is a section on the line A-A of FIG. 17; and

FIG. 19 is a sectional elevation of another form of furnace according to the present invention.

Referring to FIGS. 1 to 4, the furnace generally indicated at 1 in FIG. I comprises a combustion chamber 2 (FIG. 2) constructed of firebrick, preferably firebrick capable of withstanding temperatures of up to I700 C. to form a generally cylindrical chamber which may, for example, be some 5 feet from the mouth to the floor of the chamber and some 10 inches in internal diameter. The chamber is formed with an access port 3 to receive a conduit 4 through which liquid fuel and air are passed into the chamber as hereinbefore described. It may be seen from FIG. 3 that the conduit 4 enters the combustion chamber on a segmental line thereof and is directed at a baffle 2 formed by a line of firebricks, the baffle being curved to turn the stream of air and fuel to follow the curvature of the combustion chamber. This produces in the combustion chamber a turbulence or vortex effect and increases the residence time of the gasses in the combustion chamber. The combustion chamber is surrounded by a cylindrical brick outer casing 5 forming a continuous wall 6 up to a level somewhat above the height of the combustion chamber and an apertured wall 7 in which the bricks are loosely placed, above that level. The outer casing is formed with a roof 8 e.g. a metal plate, and also provides an access port to give access to a flue pipe 9, and an access port 10 in alignment with access port 3 to permit the passage through the outer casing of conduit 4. It will be seen that the outer casing forms an annular space 12 between itself and the combustion chamber and, as best seen in FIG. 2, has inlet pipes 13 built into it to admit air to the annular space in a direction substantially tangential to the exterior of the combustion chamber. The purpose of this will be described hereinbelow.

The furnace of the installation will burn any combustible liquid or semiliquid as a fuel but is particularly well suited for burning used oil, e.g. discarded engine oil and discarded cutting oil. The fuel is metered from a reservoir 14 by a device, best shown in FIG. 4, comprising a funnel 15 having a V-shaped recess 16 cut into its wall and a rigid member 17 in the form of a finger, secured towards its lowermost end to the funnel wall just below the bottom of the recess. The member 17 is carried by screw 18 passing freely through a bore in the member and a bore in the funnel and secured by a nut received on the end of the screw within the funnel. The shank of the screw carries a spring washer (not visible) so that although the member 17 is held firmly against movement when stationed, it can he moved undermanual finger pressure to vary its position. Fuel is withdrawn from the reservoir by a pump 19 (shown in outline FIG. 1) driven by an electric motor 20 and provided with a basket filter 21 at its inlet, and the fuel thus withdrawn is delivered through a conduit 22 from which a portion of the fuel passing along the conduit, is taken by a branch conduit 23 terminating in a wide bore nozzle 24 directed at the recess 16 of the funnel. The nozzle 24 directs a agitation of the fuel in the reservoir. In' practice it is desirable to maintain an agitation of the fuel since otherwise contaminants therein may settle and thus avoid being burned. The supporting structure required for the apparatus supported above or in the reservoir is not shown in the interests of clarity in the drawing and since it is clearly within the competence of the skilled person to provide such structure.

The fuel collected by the funnel passes by gravity down a conduit 25 which opens into conduit 4 through which air is forced by a compressor 26 so that the fuel drops into the forced air stream and is carried along thereby into the combustion chamber. The fuel is, therefore, received into the combustion chamber in a current of forced air.

Effluent from the combustion chamber passes into the flue pipe 9 which leads axially into the eye of a centrifugal fan 27 the output from which 'is ducted by pipe 28 into a building 29 in which heating is required.

It has been found that the fuel may contain up to 60 percent by volume of water with beneficial effect and water may be added to it, for this purpose simply by dropping mains water into the funnel through a tap 30 (FIG. 1).

In operation of the installation, combustion is started by any convenient means e.g. by depositing a heap of burning coals on the floor of the combustion chamber. The hot combustion gases issuing from the mouth of the combustion chamber cause cold air to be drawn in through pipes 13 of the outer casing to circulate upwardly around the combustion chamber and mix with the effluent combustion gases, and because the effluent combustion gases and the cold air thus introduced have a vortex or turbulent motion or circulatory motion, the effluent combustion gases are efficiently mixed with the cold air to the flue pipe. As a result, the temperature of the mixture at the eye of the centrifugal fan is about 130 C. i.e. a temperature harmless to the fan. This input to the fan constitutes only part of the input and further cold air is drawn thereinto directly and mixed with the efiluent from the flue pipe 9 to produce a temperature of the output from the fan of about 60 C. In one experiment, using about 2 gallons/hour of used vehicle-engine oil with about 1 gallon/hour of water added thereto, the combustion products/cold air mixture in flue pipe 9 entered the centrifugal fan at about 130 C, the flue pipe being of 18 inches diameter. The centrifugal fan had a nominal capacity of 17,000 cu.ft./min. and the temperature of the output was about 55 C. The fan was an ordinary commercial centrifugal, ventilator type without special heat resistant materials, an it remained quite unharmed. In that experiment, the building into which the output of the centrifugal fan was ducted, was a brick-drying shed and the centrifugal fan output was passed directly under the floor of the building and allowed to rise through apertures therein. It was found that the air thus introduced was completely odorless and without any noxious effect on people working in the shed. In the above-mentioned experiment, the compressor illustrated by compressor 26 (FIG. I), delivered air at about 350 cu.ft./min. under a pressure of some 2%inches of water (gauge) and the combustion chamber was feet in depth from mouth to floor and of inches internal diameter.

The fuel-buming capacity of the illustrated furnace may be varied by varying the flue aperture size of the combustion chamber and this may be done by means of a butterfly valve BF located in pipe 9 and shown in outline in FIG. 1. The more the valve is moved towards a vertical position the less becomes the fuel burning capacity of the combustion chamber and conversely, the more the valve is moved towards a horizontal position, the greater becomes the capacity of the combustion chamber until the maximum is reached when the valve assumes a horizontal position.

Although a metering arrangement as shown in FIG. 4 is extremely efiicacious, even simpler arrangements may be adopted as shown in FIGS. 5 to 8 although the principle of operation remains the same, namely, to divide a stream or jet of the fuel into two or more parts and to collect one or more the parts or to spread the stream into a sheet and collect part of the sheet according to the amount of fuel needed. In the arrangements of FIGS. 5 to 8 the jet or stream of fuel is provided by the output of conduit 22 and the conduit 23 is dispensed with. In the arrangement of FIGS. 5 and 6 fan-shaped tray 31 is secured to the end of the conduit 22 to cause the effluent stream therefrom to flow down the tray and the tray is formed at its furthermost edge with a series of indentations 32 which cause the stream flowing off the tray to be divided up into a number of separate streams. The indentations may be fonned by serrations or corrugations or simply by saw cuts made in the furthunnost edge. The collector is constituted by a further tray 33 pivoted to the funnel so that it can be swung under the tray 31 as shown in FIG. 5 to receive any number of the separate streams, the fuel thus collected draining down the tray 33 into the funnel 15. The tray 33 is pivoted to the funnel by a pin 34, on a bracket 35 (shown in outline in FIG. 6) welded or otherwise secured to the wall of the funnel, and the pin between the bracket and the tray 33 carries a helical spring 36 so that although the tray is firmly held when stationed, it can readily be moved under manual finger pressure to any desired station. The arrangement shown in FIG. 7 is similar except that the effluent from the conduit 22 is directed on the apex of a vertically held cone 37 which flares out somewhat at the bottom and is serrated at the bottom edge 37. An advantage of this arrangement is that separate feeds can readily be taken for several burners simultaneously by using a plurality of trays 33 each pivoted to a separate funnel. Instead of the tray 33 and funnel 15, however, a conduit 38 (FIG. 8) may be used as a collector, having an extending piece 39 such that the piece 39 can be extended from the conduit 38 to lie under part of the bottom edge of the cone 37 and retracted therefrom to discontinue the fuel supply. The extending piece is terminated obliquely as shown in FIG. 8 so that it can catch a separate stream falling from the cone and it is held in its extended or retracted station by a screw 39 passing through a tapped bore in the conduit 38.

In a further embodiment of the present invention, illustrated in FIGS. 9 and 10, an installation is provided which is particularly well suited to burning as a fuel to produce useful heat, rubber in the form of tires per se i.e. discarded tires.

The combustion chamber indicated at 40 is of a generally cylindrical shape and is fonned of firebrick 41, hearing externally a layer of insulation 42 consisting of vermiculite and cement fondu, and is housed in a metal casing 43. The chamber is provided with an inlet 44 in the general form of a slot in an end wall 45 and with a flue exit 46 in the opposite end wall 47. The floor of the chamber departs from the cylindrical form of the rest of the chamber and descends by steps 48 into a wall 49 constituting an ash pit, to which access is provided through a door 50 in the metal casing. Forced air is provided by a compressor 51 through three inlets passages shown in outline in FIG. 10) in the combustion chamber, one passage 52 providing forced air in the ash pit, one passage 53 at the right-hand side of the chamber as viewed from the inlet side of the installation (FIG. 10), in the floor of the chamber directing forced air segmentally upwards therein, and one passage 54 in the left-hand side of the chamber as viewed from the inlet side of the installation directing forced air horizontally across the chamber inlet so that immediately the leading part of a tire is received through the inlet slot 44 it is subjected to the current of air from passage 54. The inlet passage 53 is joined by a smaller passage 55 (shown in outline) through which water may be passed to be entrained in the forced air stream in inlet passage 53. The tires, generally indicated at 56, are fed, one after another, to and through the inlet slot 44 by an endless conveyor comprising two chains 57, 58 consisting of ordinary chain links 59 connected by metal straps 60 to which are secured bars or slats 61 to extend between the two chains; the chains being carried round sprockets 62 one of which is driven by a belt 63 from a reduction-gear box 64 in turn driven by a belt drive from an electric motor 65, to give a forward speed of the conveyor such that the tires are introduced at a rate equal to the rate at which they are burned.

The flue exit of the combustion chamber leads into a pipe 66 to conduct the effluent gases to a tubular head exchanger 67 which receives material to be heated, by passage through the tubes 68 indicated in outline in FIG. 9, through an inlet pipe 69. The material passing through the tubes 68 is discharged through pipe 70 and the cooled effluent gases are discharged through pipe 71.

Water may be fed onto the tires before entry to the combustion chamber from the mains supply through a tap 72 although if water is to be introduced with the tires any other means may be used for depositing water thereon.

In operation of the above-described tire-burning installation, combustion may readily be started by dousing the leading part of the first tire with an easily ignited fuel, e.g. petrol and igniting the fuel. The forced air supply to the combustion chamber not only provides a current of forced air for the tire as it enters the chamber but also gives rise to a turbulent or vortex movement of the gas stream in the combustion chamber thereby increasing the residence time of the gaseous materials and particles of the tyre entrained therein. As a result combustion is substantially complete by the time the combustion products are discharged from the chamber into the flue pipe 66. In one experiment with an installation as above described, a combustion chamber was employed of dimensions of some 5 feet in axial length-from the inner surface of one end wall to the like surface of the other end wall and some lfoot in internal radius giving a height of some 5 feet from the floor of the ash pit to the interior surface of the roof of the combustion chamber. Water was supplied at a rate of 12 gallons/hour mostly by deposition on and within the tires and the compressor supplied air at approximately 3200 cu.ft./min. under a pressure of some 2% p.s.i. gaugepressure to provide approximately one third this amount in each inlet passage. Tires were burned at about 720 lbs/hour to give an effluent tempt temperature of from 800 to 850 C. in respect of the combustion gases effluent from the combustion chamber and about 100 C. in respect of the combustion gases effluent from the heat exchanger.

The installation shown in FIGS. 9 and 10 may employ a furnace with a vertically aligned combustion chamber as shown in FIG. 11 rather than the furnace with the horizontally aligned combustion chamber as shown in FIGS. 9 and 10. The furnace of FIG. 11 differs in material respect only in that the combustion chamber is vertically aligned and provides the flue at the top rather than at the side. Accordingly, the parts of the furnace are indicated by the same reference numerals as are employed in FIGS. 9 and 10 for the analogous parts and it is believed that no further description is required.

FIGS. 12 to 14 show an installation of the present invention which is particularly intended to burn town refuse. The furnaoe thereof generally indicated at 73 provides a cylindrical, vertically aligned combustion chamber 74 (FIG. 13) formed of firebrick with an external insulating layer (not shown) of cement fondu and vermiculite. The bottom of the combustion chamber constitutes an ash pit access to which is provided through a door 75 in a metal casing 76 housing the combustion chamber, and the top provides the flue, opening directly to atmosphere. The cylindricalwall of the furnace provides a vertical, slotlike opening 77 (FIG. 13) through which the refuse to be incinerated is introduced. Immediately adjacent the opening 77is a rectangular recess 78 bearing a slit 79 through which forced air is introduced by a compressor (not shown), the recess and the slit giving the forced air a direction which converges with the line of motion of refuse introduced through opening 77 so that the refuse introduced almost immediately encounters forced air current on entry to the combustion chamber. As with the above-described installations, the forced air current appears to give rise to a turbulence or vortex effect in the combustion chamber. The slit 79 is the only inlet to the combustion chamber for the forced air which is supplied by the compressor through a pipe 80 to a triangular-shaped cowling 81 for the slit 77. An aperture (not shown) is provided in the outer casing of the furnace of the ing carries a chute 94 to surmount the passage access to which is provided from the chute by an aperture (not shown) in casing 93. Refuse is dumped into the chute and with the ram fully retracted passes down into the passage formed by casing 93. The refuse may be compressed and it may at this stage be sprayed with water and/or with liquid fuel such as discarded engine oil. The ram on extension, then pushes the refuse forward into the combustion chamber at the required rate of feed. This may be done intermittently but in the present embodiment, the movement of the ram is continuous and is effected by a conventional control mechanism comprising a valve unit 95 through which hydraulic fluid is fed to the ram 92 from a drum 96 thereof by a pump 97 driven by an electric motor 98. The valve unit provides a valve 99 to control the fluid supply for the expansion movement of the ram and a valve 100 to control the fluid supply for the retraction, the valves being alternately operated by a control rod 101. The control rod is pivoted to a lever 102 which is moved to operate the control rod by a pivoted weight 103. The pivoting of the weight is determined by the movement of a beam 104 through which movement of the ram is transmitted via a connecting beam 105, to the plug or piston of the device. When the ram reaches the limit of its expansion, the weight 103 goes overcentre in one direction and operates the control rod to close valve 99 and open valve 100 and when the ram reaches the limit of retraction as shown in FIG. 12, the weight goes overcenter in the opposite direction and operates the control rod to open valve 99 and close valve 100 thus starting a fresh expansion movement of the ram. Since the ram bears no load in retraction, the movement is effected rapidly but in expansion the speed is controlled by a suitable valve choice to give feed rate of the refuse substantially equal to its rate of consumption. It will be understood that normally the chute is filled with refuse when ever it empties and that it is not necessary nor normal practice to await retraction of the ram before placing a fresh load of refuse in the chute.

The above apparatus may also be used for burning tires, or tires and refuse together and, as intimated above, liquid fuel may also be incinerated simultaneously. It is not necessary to use water for incinerating any of these materials but water assists combustion and is preferably used. It may be introduced into the forced air supply and/or deposited on the refuse. The furnace may readily be started by the use of petrol or by burning coals.

Inperformance the refuse-buming installation is similar in material-burning capacity in relation to combustion chamber volume as the oil-buming and tire-burning installation hereinbefore described.

As disclosed in connection with the oil-burning installation, the fuel-burning capacity of the combustion chamber can be varied by varying the size of the flue aperture and in the case of a vertically aligned combustion chamber discharging at the top, the flue aperture may be varied by adopting either of the structures shown in FIGS. 15 and 16 respectively.

In the structure of FIG. 15, the combustion chamber top comprises a metal ring 106 to seat on the top of the cylindrical same form and in alignment with the slit 77 and the aperture is surrounded by a structure 82 secured to the outer casing and serving as a guide to position the cowling S1 at the aperture by vertical flanges one of which 83 is seen in FIG. 12, and horizontal flanges 84, 85. The cowling is secured to the horizontal flanges by lugs 86, 87 passing into respective holes provided by those flanges, and held against pivoting movement by a tie rod 88. The cowling bears a tube 89 opening thereto so that water may be introduced with the air, and a further inlet terminating in a funnel 89 so that liquid fuel may if desired be introduced and burned along with the refuse.

The opening for entry of the refuse is also surrounded by a cowling 90 lined with firebrick, into which cowling opens a device for feeding refuse to the combustion chamber. The device comprises a plug or piston 91 operated by a hydraulic ram 92 as hereinbelow described, the plug or piston working in a rectangular passage formed by a metal casing 93. The caswall of the combustion chamber. The ring provides, spaced circumferentially round the ring, a plurality of inwardly directed lugs 107 (indicated in outline) to which is keyed a firebrick, fondu cement crown 108 shown in vertical section, former with a central aperture 109 which represents the maximum flue aperture size. The ring also bears on its outer aspect a plurality of upstanding brackets each of which carries an outwardly projecting lug for the purpose of lifting the ring; the brackets being spaced so that when the ring is lifted, it is evenly balanced. One of the brackets 110 with its lug 111 may be seen in FIG. 15. In order to reduce the size of the aperture, one or more rings 112 of firebrick cemented together with fondu cement are built into the aperture and if the aperture size is. subsequently to be increased, one or more of the firebrick rings is or are removed. The aperture 109 provided in the crown 108 has the form of a transverse section of a cone and accordingly each firebrick ring is built in the same form to provide the top with greater mechanical strength. It will be understood that when it is desired to install or remove a firebrick ring, the top is removed from the combustion chamber to enable the work to be done, the top being lifted by the lugs 111 by any suitable lifling gear.

In FIG. 16, the structure consists of a ring and flrebrick, cement fondu crown as in the structure of FIG. but in this instance, the aperture of the crown is varied by a vermiculitefondu cement plug 113 cast on a metal-anchoring member 114 pivoted to a lever 115 which itself is pivoted intermediate its ends to an upstanding post 116 which may be secured to the casing of the furnace or held in some supporting structure located on the ground. By raising and lowering the plug 114 the annulus formed between the plug and the crown is varied in size. The raising and lowering of the plug may be effected by counterweighting the lever 115 in any convenient manner or by attaching it by cable to a hand winch operated from the ground. With the structure of FIG. 16 the flue aperture size can be varied at any time i.e. during the sue of the furnace.

In accordance with the present invention, a furnace may be provided in which the combustion chamber has a flue outlet in the floor thereof constituting the sole flue outlet from the combustion chamber. As a result, heat is directed down into the floor and combustible material may be deposited on the floor to be burned thereon. In this case, however, it is desirable to clear the floor of ash continuously and this may be achieved by a furnace constructed as shown in FIGS. 17 and 18. The furnace comprises a domed, cylindrical combustion chamber of firebrick 117, insulated with a layer 118 of vermiculite and fondu cement, and provided with a metal outer casing 119. The furnace further comprises inlet passages 120 arranged to direct forced air along segmental paths in the combustion chamber, and an inlet aperture 121 and feed device 122 for the input of combustible material. The floor 123 of the combustion chamber is formed separately from the domed, cylindrical portion and is set up on rollers 124 so as to be able to rotate thereon. For this purpose, the floor may be driven by a pinion (not shown) meshing with a toothed ring 125 provided on the outer aspect of the rotary floor. As shown in FIG. 17 a sand seal 126 is provided between the floor and the upper portion of the combustion chamber although in practice the furnace can be operated satisfactorily without the seal. The floor has a central flue aperture 127 and is dished to provide a shallow inclination from the periphery to the central aperture. The dished part of the floor has grooves 128 formed therein, the grooves having a curvature in the direction of motion indicated by arrow R (FIG. 18). It is found that material burning on the floor when making contact with the cylindrical wall of the combustion chamber tends to be halted and as a result push ash down the grooves to the central aperture. The floor, therefore, is selfcleaning. The combustible material opening to the combustion chamber is provided with a forced air inlet 129 as described above in connection with the refuse burning installation and because combustion takes place rapidly on the rotary floor as well as within the combustion chamber at the opening, a higher rate of feed of combustible material can be achieved. The ash falling through the central aperture falls into a water quench 130 and the flue gases leave by a flue pipe 131. The water quench is periodically cleared of ash, by a scraper chain 132 taken up on and payed off from respective winches one of which 133 is shown in FIG. 17.

A bottom flue may also be used in a combustion chamber having a top flue as illustrated in FIG. 19 and a furnace of this kind lends itself to the use of the bottom flue for the heat treatment of materials. The material may be stone chips which need to be reduced in size and, as an alternative to crushing, the chips may be broken up by exposing them to the heat from the combustion chamber below the bottom flue. Referring to FIG. 19, a rotary table 134 is provided to rotate on a central post 135 on being driven through a toothed ring and pinion mechanism indicated at 136. The table is so positioned that a part of the table always lies under the bottom flue 138 of the combustion chamber 139 while a diametrically opposed part always lies clear of the combustion chamber. The chips 140 are deposited and spread out on the latter part so as to be able to pass under the combustion chamber and are brought by rotation of the table, under the bottom flue. A period of seconds usually suffices to cause fracture of the chips and the table may, therefore, be kept in continuous rotation. The continued rotation of the table, brings the chips in their fractured condition clear of the combustion chamber when they may be swept off from the table by any convenient means.

The combustion chamber illustrated is formed of flrebrick 141, insulated by a layer 142 of vermiculite and cement fondu and housed in a metallic outer casing 143. It is intended to burn oil e.g. discarded engine oil, which is introduced in a forced air stream in the manner described in connection with the installation of FIGS. 1 to 4, through inlet conduit 144 or conduit 145 or both simultaneously. The top and bottom flues are provided by apertured domes 146, 147 formed respectively at the top and bottom of the combustion chamber with flrebrick and cement fondu. An advantage of the domed shape at the bottom of the chamber is that it acts as a channel to receive any unbumt fuel falling from either inlet conduit. Although the furnace illustrated is intended for a liquid fuel, it will be understood that the top and bottom flue arrangement may also be used in a furnace for burning tires and/or refuse. It will be understood that a combustible material inlet may be provided in any position in the upstanding wall of the combustion chamber e.g. midway between top and bottom, either as the sole combustible material inlet or as one of them.

As intimated above, the combustible materials mentioned above in connection with the various installations may have various other materials burnt with them such as chemical sludges, sewage, coal slack and combustible fines. However, any waste material of a suitable calorific value may be burnt as the sole material.

The embodiment of the present invention using top and bottom flues may also be used for burning the rubber off tires in order to recover the metal rings therein. Thus, a tire is positioned below the flue to cause the rubber to ignite and burn away and leave the metallic parts of the tire which are then removed and replaced by a fresh tire.

We claim:

1. An incinerating furnace comprising a refractor-lined substantially cylindrical combustion chamber having an axial length several times its inner diameter and having a flue outlet coupled to one end thereof; means for feeding combustible material into said chamber; and means for introducing forced air into said chamber, said air-introducing means including an air inlet duct adjacent to the other end of said chamber oriented to direct air into said chamber generally tangentially of said chamber for inducing a vortex longitudinally of said chamber and means for causing a stream of air to impinge upon said combustible material while entering the chamber, and means controlling the flow of air into said chamber so that the rate of supply of air sufi'rces but does not substantially exceed that which is required for complete combustion of said combustible material within said combustion chamber.

2. A furnace in accordance with claim 1, further comprising means for inducing vortex flow to the gases in said flue outlet.

3. A furnace in accordance with claim 1, further comprising means for varying the effective passage area of said flue outlet.

4. A furnace in accordance with claim 1, further comprising a heat exchanger coupled to said flue outlet for utilizing the flue gases thereof.

5. A furnace in accordance with claim 1, further comprising means for supplying controlled amounts of water to said combustion chamber along with the combustible material.

6. A furnace in accordance with claim 1, further comprising a structure surrounding the path of gaseous combustion products efiluent through said flue outlet, said structure having vents for admitting air thereto so that the draft of the gaseous combustion products passingalong said path draws fresh air in through the vents to mix with the eflluent gaseous combustion products.

7. A furnace in accordance with claim 6, wherein said vents are arranged in relation to said path so that the fresh air before joining the eflluent gaseous combustion products is given vortex flow.

8. a method of operating an incinerating furnace having a refractor-lined substantially cylindrical combustion chamber of an axial length several times its inner diameter and having a flue outlet coupled to one end thereof, comprising feeding combustible material into said chamber, introducing forced air into said chamber to provide a stream of said air adjacent to the other end of said chamber oriented to direct air into fed to the furnace at a rate not exceeding the rate at which it is consumed. 

2. A furnace in accordance with claim 1, further comprising means for inducing vortex flow to the gases in said flue outlet.
 3. A furnace in accordance with claim 1, further comprising means for varying the effective passage area of said flue outlet.
 4. A furnace in accordance with claim 1, further comprising a heat exchanger coupled to said flue outlet for utilizing the flue gases thereof.
 5. A furnace in accordance with claim 1, further comprising means for supplying controlled amounts of water to said combustion chamber along with the combustible material.
 6. A furnace in accordance with claim 1, further comprising a structure surrounding the path of gaseous combustion products effluent through said flue outlet, said structure having vents for admitting air thereto so that the draft of the gaseous combustion products passing along said path draws fresh air in through the vents to mix with the effluent gaseous combustion products.
 7. A furnace in accordance with claim 6, wherein said vents are arranged in relation to said path so that the fresh air before joining the effluent gaseous combustion products is given vortex flow.
 8. a method of operating an incinerating furnace having a refractor-lined substantially cylindrical combustion chamber of an axial length several times its inner diameter and having a flue outlet coupled to one end thereof, comprising feeding combustible material into said chamber, introducing forced air into said chamber to provide a stream of said air adjacent to the other end of said chamber oriented to direct air into said chamber generally tangentially of said chamber for inducing a vortex longitudinally of said chamber and to cause a stream of said air to impinge upon said fuel while entering the chamber, and controlling the flow of air into said chamber so that the rate of supply of air suffices but does not substantially exceed that which is required for complete combustion of said fuel within said combustion chamber.
 9. A method as set forth in claim 8, wherein the material is fed to the furnace at a rate not exceeding the rate at which it is consumed. 